As is known, integrated circuits are used in a wide variety of electronic equipment, including portable, or handheld, devices. Such handheld devices include personal digital assistants (PDA), CD players, MP3 players, DVD players, AM/FM radio, a pager, cellular telephones, computer memory extension (commonly referred to as a thumb drive), etc. Each of these handheld devices includes one or more integrated circuits to provide the functionality of the device. For example, a thumb drive may include an integrated circuit for interfacing with a computer (e.g., personal computer, laptop, server, workstation, etc.) via one of the ports of the computer (e.g., Universal Serial Bus, parallel port, etc.) and at least one other memory integrated circuit (e.g., flash memory). As such, when the thumb drive is coupled to a computer, data can be read from and written to the memory of the thumb drive. Accordingly, a user may store personalized information (e.g., presentations, Internet access account information, etc.) on his/her thumb drive and use any computer to access the information.
As another example, an MP3 player may include multiple integrated circuits to support the storage and playback of digitally formatted audio (i.e., formatted in accordance with the MP3 specification). As is known, one integrated circuit may be used for interfacing with a computer, another integrated circuit for generating a power supply voltage, another for processing the storage and/or playback of the digitally formatted audio data, and still another for rendering the playback of the digitally formatted audio data audible.
Integrated circuits have enabled the creation of a plethora of handheld devices, which may link to one another. For example, one may link any combination of the following devices: a cellular telephone, a PDA, one or more thumb drives for extended memory functionality, an MP3 (audio or multimedia) player for storage and/or playback of digitally recorded media. To ensure proper connections between devices, termination impedance (e.g., a resistor) is used to ensure each device can properly interface with one another. To do this, the terminal resistor needs to be a precision resistor (e.g., a tolerance of +/−5%), which is very difficult to achieve in an acceptable die area of an integrated circuit.
Therefore, a need exists for integrated circuits that establish impedances (such as termination impedances) within specific predetermined values.